The present invention relates generally to a powder spray coating system, and in particular, to a quick-change powder spray coating system.
Powder spray coating systems are commonly used to powder coat various consumer products, typically metal, wood or plastic, such as office furniture, including for example storage units, and other general industrial powder coat applications, including for example, various automotive products and the like. In order to maintain smaller inventories while at the same time providing a wide selection of colors to the end user, it often is necessary and desirable to change the color being applied to one or more products several, dozens or even hundreds of times during a typical eight-hour shift. Typically, a hopper is used to supply the powder to one or more spray guns being used to apply the powder. When a color change is desired, the operator ordinarily is required to purge the powder supply lines and vent tubes connected to a supply hopper so that residue powder in the lines does not contaminate the next color, or product being sprayed therewith. The operator then must disconnect the various air lines, fluidizing lines, vent tubes, and powder hoses from the hopper and reconnect the various lines and hoses to a new hopper. Even with skilled operators, such changes can take several minutes.
To avoid some of the difficulties associated with color changes, some manufacturers use a different, dedicated paint line and spray gun for each color. However, many manufacturers run ten or more colors, which can thereby prohibitively increase the expense and space required to maintain such equipment.
Other manufacturers have developed systems that provide a plurality of supply hoppers feeding one or more spray guns, as shown for example in U.S. Pat. No. 6,112,999. Such systems, however, require the powder supply line to be disconnected from the gun and back purged to the supply hopper. However, if residue from a different color remains in the line, it may be purged back into the supply hopper, thereby contaminating the entire hopper. Moreover, such systems do not provide for the spray gun to be purged, which also can lead to contamination when the spraying operation is resumed. Moreover, such systems incorporate complicated control systems, which can be expensive to construct, maintain and operate.
Briefly stated, in one aspect of the invention, one preferred embodiment of a powder spray system comprises a plurality of supply hoppers, a purge air supply, a manifold operably connected to each of the plurality of supply hoppers, and a spray gun. The manifold comprises a plurality of outlets. The spray gun is operable in a plurality of spraying configurations and a purging configuration. The spray gun is selectively, removably connected to at least one of the outlets when in one of the plurality of the spraying configurations and is removably connected to the purge air supply when in the purging configuration.
In a preferred embodiment, the spray gun comprises a hose that extends therefrom and terminates in an open end. The open end is selectively, removably connected to at least one of the plurality of outlets when the spray gun is in the spraying position. The open end is removably connected to the purge air supply when the spray gun is in the purging position.
Also in a preferred embodiment, the system further includes at least one main air supply connected to the manifold and a plurality of air supply lines connecting the plurality of supply hoppers and the manifold. The manifold further comprises a plurality of valves each moveable between at least an open position and a closed position. The plurality of valves correspond to and are operably connected to the plurality of air supply lines. The main air supply communicates with at least one of the supply lines, and preferably two supply lines, when at least one of the valves corresponding to that supply line or lines, and preferably a set of valves, is in the open position.
In another aspect of the invention, a fluidizing air supply is connected to each of said plurality of supply hoppers. A vent box comprises a plurality of inlets connected to the plurality of supply hoppers.
In yet another aspect of the invention, a method of operating a powder spray system includes connecting the spray gun to one of the plurality of outlets, supplying air to one of the supply hoppers associated with the selected outlet connected to the spray gun, and spraying powder from the supply hopper. The method further includes disconnecting the spray gun from the selected outlet, connecting the spray gun to a purge air supply and purging the spray gun with the purge air supply. The spray gun is then connected to another of the plurality of outlets.
The present inventions provide significant advantages over other powder coating systems and methods for applying powder coating. For example, the system provides for a plurality of supply hoppers to be operably connected to a manifold. As such, individual hoppers do not have to be disconnected and removed after each color change cycle. Rather, one or more valves, preferably two, can be quickly and easily turned to isolate any particular hopper. In addition, the spray gun can be quickly removed from its connection with any one hopper. The spray gun, and any line extending therefrom, can be quickly purged between color changes so as to avoid contaminating either the next product to be sprayed and/or the supply hoppers. The spray gun can then be operably reconnected to the next hopper for a new spraying cycle with a new color. As such, the system avoids back purging, which can contaminate the supply hoppers, while at the same time allowing for the spray gun to be purged. The system is simple and robust and does not require expensive and difficult to maintain control systems. In addition, color changes can be effected by a single operator in about 10 seconds, or even less, with minimal waste and no risks of contamination.
The vent box, with its plurality of inlets, also provides significant advantages. In particular, it allows one or more supply hoppers to be vented to a single location. At the same time, all of the hoppers can be fluidized, even when not in use. As such, construction, maintenance and operation costs are reduced.
The present invention, together with these and other advantages, will be best understood by reference to the following detailed description taken in conjunction with the accompanying drawings. The foregoing paragraphs have been provided by way of general introduction, and should not be used to narrow the scope of the appended claims.